1. Background Art
The present invention relates generally to sample transfer systems and, more particularly, to a novel sample transfer system which employs a plurality of pipettes to transfer simultaneously samples between welled trays.
2. Background Art
One of the primary requirements in laboratory research, especially in the biotechnology and medical fields, is to transfer small aliquots of various liquids from one container to another. Such transfers may be made through the use of individual or multiple pipettes. As the sensitivity of the testing protocols has been increased, the volume of reagents and samples has been reduced to microliter quantities. Today, the de facto standard for biotechnological and medical research fields is a 96-well protocol using an array of small wells in a thermoplastic tray. The wells, holding up to 300 microliters per well, are usually arranged in an 8.times.12 matrix on 9-mm centers.
Typically, the user pipettes the sample or reagent volumes into these wells. Individual volumes range from 1 microliter up to the 300 microliters required to fill the volume of the well. For those protocols that require higher volumes, a deep well container is used in which each well holds 1 to 2 ml. These deep wells may be individual tubes or they may be formed as a molded unit. However, they are also usually arranged in the standard 8.times.12 matrix on 9-mm centers to take advantage of the variety of automated and manual devices that have been developed around this standard.
The sample transfer devices range from individual manual pipettes to multiple pipettors handling a row of 8 or 12 samples at a time. The manual devices have been augmented by automated devices that process complete sets of 96 samples by indexing the sample plate one row at a time under the pipetting device. Robotic arm assemblies and X-Y-Z bridge assemblies have added further automation and flexibility of processing. However, even the latter are relatively slow, in that not all wells are serviced simultaneously.
The necessity of preventing cross-contamination between samples has led to the use disposable tips on the end of the pipettor assemblies. Packaging has allowed these tips to be loaded individually or in rows of 8 or 12 using manual or automatic means. Generally, the tips are held to the pipettors with a tapered friction fit that (1) seals the connection, and (2) allows the tip to be ejected manually or automatically, though some employ a double O-ring arrangement that both seals and holds the tips in proper orientation. The latter do not provide means for automatic tip ejection.
The testing protocol's sensitivity has placed increased importance on the accuracy of the liquid transfer device. Most pipetting devices today use an air displacement method of aspirating or dispensing liquid. The newer devices use positive displacement, minimizing the volume of any compressible fluid, such as air between the sample and the displacement plunger or device.
These advances in the technology make it economical to process a higher number of samples. However, each new level of testing encounters some area of resistance to the desired higher throughput. Presently, the limiting factor is reading endpoints on pipettes. However, new developments are being developed to quickly and economically read 96 samples with colorimetric or radiometric means. With these advances, the throughput limitation becomes sample preparation and processing. No known transfer device provides for the selective use of either air displacement or positive displacement liquid transfer methods with a single apparatus. None provides for fully programmable sequencing of tip insertion, liquid transfer, and tip ejection.
Accordingly, it is a principal object of the present invention to provide method and means for the simultaneous transfer of a plurality of liquid samples which method and means employs a device which provides for the selective use of either air displacement or positive displacement liquid transfer.
It is a further object of the invention to provide such method and means which can be programmed for the sequence of tip insertion, liquid transfer, and tip ejection.
It is another object of the invention to provide method and means for the simultaneous mounting of a plurality of tips to a pipetting device.
It is an additional object of the invention to provide method and means for the simultaneous ejection of a plurality of tips from a pipetting device.
A further object of the invention is to provide the foregoing methods and means which are economically constructed and used.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.